The embodiment relates to a light emitting device, a method of manufacturing the same, a light emitting device package, and a lighting system.
An LED (light emitting device) is an element that converts electric energy into a light energy. For instance, the LED can produce various colors by adjusting the compositional ratio of compound semiconductors.
According to the related art, an LED based on a nitride semiconductor, such as a GaN epitaxial layer, has been used.
Meanwhile, according to the related art, a sapphire substrate of a SiC (silicon carbide) substrate has been used extensively used for growing GaN. Recently, studies and research have been performed to use a silicon substrate having the price competitiveness as a substrate for growing GaN.
The silicon substrate is advantageous in terms of the price competitiveness, large-size, electric conductivity and thermal conductivity.
However, the silicon substrate represents the disadvantages in that many defects and cracks may exist in a GaN layer due to the great difference in lattice constant and thermal expansion coefficient between silicon (Si) and gallium nitride (GaN).
For instance, according to the related art, the crack is generated in a GaN epitaxial layer when the GaN has been grown on the silicon substrate due to the tensile stain, which is generated during the cooling process caused by the difference in thermal expansion coefficient between the GaN, which is grown under the high temperature, and the silicon substrate.
In addition, silicon (Si) of the silicon substrate may react with TMGa, which is an element of the GaN, to form gallium silicide, so that melt-back is formed on the surface of the silicon substrate.